The DBLINK line is used to link other databases for BioProject ID, Sequence Read Archive and so on.

DDBJ has replaced the PROJECT line by DBLINK line format since 2009, because there are other resources than project IDs.

example
DBLINK      BioProject:PRJDA12345
            Sequence Read Archive:DRR012345, DRR012346

BioProject －－ The name of linked database; BioProject database

PRJDA12345 －－ Linked ID in the database; BioProject accession number

Sequence Read Archive －－ The name of linked database; Sequence Read Archive (SRA)

DRR012345, DRR012346 －－ Linked ID in the database; SRA Run accession numbers